1. Field of the Invention
The present invention relates to a screen printing apparatus, in particular, to an apparatus in which a squeegee is provided for uniformly providing ink to a printing plate.
2. Background Art
Screen printing is a process: for conducting printing by means of transferring ink which is passed through the ink penetrating portion of the printing plate to a sheet material by means of first placing the printing plate which is fixed within a housing onto the sheet material to undergo printing, filling the housing with printing ink, and then rubbing ink onto the printing plate using a spatula-shaped rubber material known as a "squeegee". The printing plate which is generally used is produced by means of forming a print layer such as a resist layer or the like onto a mesh screen which is woven using nylon, polyester, stainless steel, or the like, by means of a photochemical process. In this manner, the eyelets of this screen are partially blocked, thereby forming an ink penetrating portion in the shape of the print.
By means of screen printing, the ink maintained inside the ink penetrating portion of the printing plate is adhered to the sheet material by means of the squeegee, and thus a comparatively thick film can be formed corresponding to the thickness of the printing plate. With regard to this point, screen printing is superior to other printing methods such as letter-press printing, lithography, and the like. With a thick film, not only is three-dimensional printing possible, but also this film may be practically applied to the manufacture of etching resists and print substrates for use in semiconductor production. The technology for producing thick films can be applied to a wide range of fields, and thus there is a growing demand for this technology within various industrial fields. However, conventional screen printing apparatuses spread ink by means of moving the squeegee in only one direction after ink is placed on the printing plate. Therefore, if the thickness of the printing plate is increased to greater than the present state, it will be difficult to uniformly rub ink over the entire region of the ink penetrating portion formed in the printing plate. For example, according to the aforementioned method, disadvantages are generated such as smudging of the print at the section along the back-end edge of the ink penetrating portion with respect to the squeegee direction of movement due to an insufficient ink packing density.
It is an objective of the present invention to provide a screen printing apparatus which can uniformly pack ink into the ink penetrating portion, even in the case when the thickness of the printing plate is large, such that a printing image of a high precision possessing a large film thickness can be formed.